This invention relates to medical treatments for biological concretions and more specifically, to devices and methods for entraining and extracting these concretions such as urinary, biliary, and pancreatic stones, and other calcified material or debris from the body.
Urolithiasis, or kidney stone disease, is a significant health problem in the United States. It is estimated that between 2-5% of the general population will develop a urinary calculus during their lifetime. Since being introduced in the 1980s, minimally invasive procedures such as lithotripsy as well as ureteroscopy have become the preferred methods for treatment in a majority of cases of stones in the ureter, and have a potential for application to concretions that develop in other parts of the body such as the pancreas and the gallbladder.
Lithotripsy is a medical procedure that uses energy in various forms such as acoustic shock waves, pneumatic pulsation, electrical hydraulic shock waves, or laser beams to break up biological concretions such as urinary calculi (e.g. kidney stones). The force of the energy, when applied either extracorporeally or intracorporeally, usually in focused and continuous or successive bursts, comminutes a kidney stone into smaller fragments that may be extracted from the body or allowed to pass through urination. Applications to other concretions formed in the body, such as pancreatic, salivary and biliary stones as well as the vascular system, are currently underway in several research laboratories across the United States and Europe.
With the help of imaging tools such as transureteroscopic videotechnology and fluoroscopic imaging, the operator of the lithotripter device can monitor the process of the procedure and terminate treatment when residual fragments are small enough to be voided or grasped and removed. Currently, more than 2000 extracorporeal lithotripter devices and thousands of intracorporeal lithotripter devices are in operation around the world and over five million treatments have been performed.
Although these promising new techniques and instrumentation have improved the treatment of kidney and other biological stones, some problems remain. For example, stones in the ureter which are treated by intracorporeal methods of fragmentation may become repositioned closer to the kidney, and it then becomes necessary to prevent retrograde, i.e. cephalad or upward, migration of the stone fragments toward the kidney. It is also desirable to be able to extract such fragments from the body with the same instrument, preventing the need for successive instrumentation.
The prior art teaches several types of stone extraction devices which are designed to extract biological concretions without the necessity of major open surgery. However, each of these devices suffers from limitations. Most of these devices comprise curved wires which form a cage or basket; see, e.g., U.S. Pat. Nos. 2,943,626, 3,472,230, 4,299,225, 4,347,846, and 4,807,626. The cage or basket-like configuration entrains a single stone within the wire frame; but these prior art devices have rigid frames that lack the maneuverability and flexibility to engage and disengage a stone repeatedly without causing harm to the surrounding tissue, and the entraining portion of these prior art devices are often rigid and are either not collapsible into a smaller configuration or require mechanisms for opening or closing the basket. If the basket or cage of the device itself has become trapped within the ureter, a second device often must be deployed to retrieve the first basket from the body; and if the basket or coil structure has entrained a stone which is too large to be extracted without further fragmentation, it also may be difficult to disengage the stone without a significant amount of manipulation.
Another prior art device comprises one or two inflatable balloon catheters that are manipulated so that the arrested stone is caught between one or more of the balloons. The balloon is slowly withdrawn from the body, and if there are two balloons, the lower balloon acts as a dilator of the ureteral wall and the upper balloon pushes the stone downward towards the bladder. See, e.g., U.S. Pat. No. 4,295,464. The balloons of such devices are difficult to manipulate and failure to maintain the balloons in the correct spatial position may result in loss of the stone. Further, if a stone is caught in a narrow passageway during the extraction process, the balloon catheters cannot move the stone away from the exit direction to dislodge it from the passageway; and if the stone is caught in between the lining of the ureteral wall and the balloon, the pressure of the balloon may push the stone into the lining, causing significant damage to the lining. Also, soft air-inflated balloons are easily punctured when used in conjunction with most types of stone fragmentation procedures.
There is a particular need, therefore, for a guidewire device that prevents upward migration of stone fragments generated during a stone fragmentation procedure, and which safely and efficiently extracts fragments from the body. Thus, a device possessing the following abilities is desired: ability to act as an energy-absorbing barrier that prevents fragments from migrating toward the kidney; ability to xe2x80x9csweepxe2x80x9d one or multiple smaller fragments downward and out of the body; the ability to engage and disengage the stone repeatedly, and the ability to disengage the stone for repositioning for further fragmentation if the entrained stone is too large to pass from the body.
Accordingly, it is an object of the present invention to provide a flexible, form-fitting device which prevents upward migration of biological stones and fragments of stones generated during medical procedures for stone fragmentation. It is another object of the invention to provide a device in which the entraining configuration may be collapsed and redeployed repeatedly as required during a stone fragmentation procedure.
A further object of the invention is to provide a device which can safely guide the one or multiple stone fragments from the body, sweeping it downward and which as a safety feature, disengages itself from a stone that is too large to pass a specific path in the body by a simple pulling motion.
The invention features a device comprising a wire core at least a portion of which is comprised of a super-elastic deformable material wound to form a helical coil which tapers from a larger diameter proximal end to a smaller diameter distal end. Because the coil portion of the core is formed of a super-elastic material, preferably a nickel titanium alloy such as nitinol, the coil has the ability to uncoil into a relatively straight configuration when retracted into a tubular sheath or pulled against an obstruction, and reform into a coil configuration when deployed, e.g. withdrawn from, a tubular sheath. In preferred embodiments, a continuous super-elastic wire core is surrounded by a wrapped helical spring, typically having two sections which are attached to each other and to the core at a midjoint proximal to the tapered helical coil. Another preferred embodiment features a layer of polymeric material covering the surface at least a portion of the device, as well as a layer of radiopaque material which covers at least a portion of the tubular sheath and/or the device.